Observation of Gravitational Waves from a Binary Black Hole Merger

[gary]

Observation of Gravitational Waves from a Binary Black Hole Merger
B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration)
Phys. Rev. Lett. 116, 061102 – Published 11 February 2016





Abstract -
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102

Full paper in PDF available under Creative Commons License -
https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102

[Shiraz]

goodness me....what a time to be alive. Thanks for posting.

so the merger resulted in three solar masses of energy being converted to gravitational waves....in a fraction of a second. And it is all as GR predicted - how extraordinary.

seems like black hole mergers make spacetime go "boing".

I wonder what the "black holes don't exist" brigade will do now.:shrug:! http://www.huffingtonpost.com.au/entry/black-holes-dont-exist_n_5885940.html?section=austra lia

[gary]

Hi Ray,

A great time to be alive indeed.

Ponder the fact that the black hole merger took place at a time
a billion years ago where we were still single cell organisms and
starting to evolve into multi-cell organisms.

The gravitational waves emanated across space at the speed of light and
by the time they reached Earth on Monday September 14th 2015 we
had evolved to the point we could detect them.

[Dave2042]

I gather that a particular aspect of this is that the observed signal shows that all the waves (at different frequencies) traveled at the same speed (c). This rules out a bunch of 'exotic' variants of GR.

Neat.

[glend]

I believe that the researchers will be exploring all possibilities of exotic variants in decades to come in 'gravitational astronomy'. Unlike light they don't seem to reflect or lense but travel right through things. If the ones observed from the binary blackhole merger took one billion years to get to us, where are all the others, there should be massive numbers of waves moving through space/time in all directions.

I can just hear people ringing work and using a gravitational wave passing through them to excuse all sorts of things - the ulimate excuse.

[Bendy]

Nicely put Gary, certainly gave me pause.

I love the following aspect of the discovery:

"The violent event temporarily radiated more energy — in the form of gravitational waves — than all the stars in the observable Universe emitted as light in the same amount of time."

http://www.nature.com/news/einstein-s-gravitational-waves-found-at-last-1.19361

[Shiraz]

nice simulation video here (and an an audio representation of the actual signal)http://www.huffingtonpost.com.au/entry/gravitational-wave-discovery-would-open-new-window-on-the-universe_us_56bb5cc7e4b08ffac123659 b?section=australia

[Eratosthenes]

Can the researchers identify the source/direction of these very faint gravitational waves? Is it a "cumulative" wave?

Very important discovery - perfect example of how the scientific method works - the interplay between theory/mathematics and experiment/observation

A huge number of scientists, research groups and institutions have been involved in the LIGO project. (e.g Lots of Russian input which spans several decades).

[gary]

There were only two interferometers active at the time, one in
Louisiana and one in Washington state.

The Virgo interferometer was offline at the time undergoing an upgrade.

As discussed in the press conference, with only two interferometers the
source could only be narrowed down to a relatively large region, somewhere
in the direction of the Large Magellanic Cloud but 1.3 billion light years
away.

Probability contour plot here -
https://www.ligo.caltech.edu/image/ligo20160211b





The video of the press conference includes a supercomputer
animation of the black hole merger and graphically shows the nature
of the disturbance that created the ripple in space-time.

[silv]

a "ripple in space time" for "a fraction of a second".

was it the low sensitivity of the 2 Ligo that shortened the measurable wave to so incredibly ... short?
I mean, 2 black holes marrying each other - that's surely a major BAM in gravity, no?
bigger than, say, a super nova?

""The violent event temporarily radiated more energy — in the form of gravitational waves — than all the stars in the observable Universe emitted as light in the same amount of time.""

both wave forms travel at speed of light but gravitational observable offspring is only 10 miliseconds? whereas last year's big super nova had a peak plateau of several days....

and if all this IS indeed so - and the 2nd LIGO, necessary to have proof, only came online 2 days before the ripple hit - that's also very incredible.

plus afterwards, nothing else worth mentioning up to January when the first observation phase ended. ... incredible.

Did Einstein throw the dice for this one?

[silv]

Shiraz, :)
I guess there is a reason for peer reviewed papers, eh?
And also a reason for papers without such quality control :p

[Eratosthenes]

wasn't a Nobel prize awarded in the 1990s (1993 or 1994?) for ground breaking work on gravitational waves?

This measurement needs to be validated by repeated detection and hopefully verified by another device in another part of the world.

Gravitational waves exist theoretically, and are a rational consequence of intense matter/energy interactions, but obviously are difficult to detect due to their faintness and minute amplitudes.

Looks like the next generation of LIGO detectors might get funding - perhaps increase the length of the evacuated tube to 6km or more. (remember, the initial funding for the LIGO detector was fought for vigorously and almost didnt get approved). One of these simple experiments but performed on ridiculously large scale looking for minute shifts in laser beam measurements. I hope they allowed for the trucks zooming on the nearby freeway or the odd earth tremor.

Just when you thought that the pathetic corporatised Scientific community, with its trivial pursuit of technological advancements approved by Wall Street short term junkies was plunging deeper and deeper into its sticky abyss of ignorance, it sneaks in some fundamental research like the LIGO experiment or the LHC search for the Higgs Boson. we are definitely wiser as a result of their results.

Who would have thunk it? Well done Kip, the gang and the Russian freak scientists in Moscow

:D

[Eratosthenes]

Scientists are very crafty when releasing news to the public prior to having it validated by the peer review process in the scientific journal system.

The purpose of Symposiums, seminars and other informal society meetings and gatherings offer plenty of opportunity to flesh out any issues with measurements and conclusions etc. These measurements after all, when not carried out a few weeks ago. IMO for the big guns to release the news, albeit with some caution, says to me that gravitational waves have indeed been detected but require validation and verification.

I am grateful that Scientists are finally dragging themselves out of the corporate pit of commercialisation and decontaminating their profession from the stench of their ignorant fear and corporate sell out.

Great to see. there is hope for science after all

:D

[xelasnave]

Why is the signal so short. The merger of objects of the masses involved shows up for only a split second if I read correctly.
I expect the answer can be found using GR but can anyone give an explanation.

Well having found GWs can they conclude GR has delivered its prediction and so stop spending money on GWs and channel funds to something even more exciting.

What benefits will acrue by pursuing GW research or having absolutely established GWs exist where does that take us.

Congratulations to those involved.

[silv]

yes, please, why so short?

[multiweb]

Cool video. Explains it well. :thumbsup:

[silv]

as to the benefit of GW: it determines which of the several current assumptions of the universe "type" are wrong, which are somewhat wrong and which are a bit right.
http://www.scientificamerican.com/article/multiverse-controversy-inflation-gravitational-waves/

or maybe that only applies to the ones still around from the bigbang. I dunno. dang I wish I had some form of scientific education. in the universe of my brain, every minute particle of understood stuff floats around unattached to and unaware of the next particle. it's utter chaos.

[Eratosthenes]

a novel way of "observing" the universe is potentially possible now.

A gravitational wave scope/detector

it may be able to detect objects and/or phenomena that are currently not understood or observable in any way.

very exciting times ahead if GW detectors and methods can be constructed with enhanced sensitivity and accuracy.

The scientific community should take one big theoretical/experimental bow today - it's the way science should function in this pathetically corporatised and casino stock market world. Scientists and decision makers should exhibit courage and imagination when performing their professional duties otherwise the stench of their pathetic craft will remain

:D

[anthony.tony]

http://www.nature.com/news/gravitational-waves-1.19321 - Some good info from Nature Magazine -- Tony.

[sjastro]

Alex,

The signal is short only because it fell within the detection limits of LIGO.

Giving a GR free explanation, gravitational waves are produced by the orbital decay of binary systems around a centre of mass.
The power radiated by a gravitational wave increases steadily as the objects approach the centre and rotate faster. There is a substantial increase in power in the very final stage leading to collision.
In the case of binaries being Black Holes there is no collision but a merger, the increase is even greater leading to a "spike" in the gravitational wave emission strong enough to be detected by LIGO.

Interestingly being a non linear theory GR is next to useless in describing the interactions between objects of similar mass, gravitational waves are an exception as has been recently shown.:)

Steven

[gary]

To gain some feel for how quickly the merger took place, the supercomputer
simulation animation given at the press conference may help be of
assistance to some readers.

Start at 33:50
https://www.youtube.com/watch?v=vy5vDtviIz0

The final merger takes 20ms.

However, as addressed in an answer to a question in the video
(go to 56:47) that last 20ms represents the signal from the final merger
when the signal rose above the noise floor of the instruments.

Long before that, as the black holes orbited each other, there would
have still been a fainter gravitational signal.

Frans Pretorius of Princeton specializes in numerical solutions of
the field equations for general relativity and came up with
the first supercomputer solution of two black holes merging only
relatively recently, in 2005.

See http://arxiv.org/pdf/gr-qc/0507014v1.pdf

He was awarded the 2010 Aneesur Rahman Prize for Computational Physics
for this brilliant work.

See https://www.aps.org/programs/honors/prizes/prizerecipient.cfm?first_nm=Frans&last_nm=Pretorius&year=2010

Shortly after the Pretorius breakthrough in 2005, a different numerical
approach was discovered and groups have been improving the accuracy of simulations ever since.

See http://w.astro.berkeley.edu/~gmarcy/astro160/papers/binary_black_hole_mergers.pdf

These simulations were able to provide the gravitational wave community
with waveform signatures to look for.

2013 talk by Frans Pretorius on YouTube -
https://www.youtube.com/watch?v=UtzJIkg3ZpM

The sound quality is poor but Pretorius discusses black hole mergers at 28:24.

"When Black Holes Collide" presentation here in PDF format -
http://www.stsci.edu/institute/itsd/information/streaming/archive/STScIScienceColloquiaSpring2009/FranPretorius021809Hi_supporting/FransPretorius021809

There are three phases to a merger - inspiral merger & ringdown.
See http://arxiv.org/abs/1102.3781

The ringdown period was predicted by the models to be damped.
See http://arxiv.org/pdf/1102.3781v1.pdf

[xelasnave]

Thank you Steven.

[xelasnave]

Thank you Gary

[Amaranthus]

During the 20ms of the merger, this event released roughly 50 times more energy than the totality of rest of the stars in the observable UNIVERSE: 3.6 x 10^49 joules/sec (200 solar masses converted to pure energy).
http://www.techinsider.io/black-hole-collision-energy-50-times-universe-2016-2

Contemplate that!

[silv]

Thank you Steven, and thank you, Gary for the URL collection and explanations!

[Steffen]

I suppose this discovery was well-vetted before publication. I think Lawrence Krauss may have blabbed about it on Twitter a month ago, then retracted it as a rumour :)

[silv]

:D

ah, no, Shiraz had linked to an article of a different kind and I'm referring to that one.

did you all read the one on TheConversation? by members of the Australian teams? I liked it over brekkie. Not scientific.
https://theconversation.com/australias-part-in-the-global-effort-to-discover-gravitational-waves-54525

[Eratosthenes]

the energy involved reflects the fact that the space-time continuum has been disturbed and measured across a vast distance, albeit a short and faint signal.

the flip side of this is that perhaps these massive energy and collision events arent very common.

I wonder if they will detect something similar in the future?

[deanm]

Why was the signal so brief?

As indicated by sjastro, the most intense GW radiation takes place just before the 'merge' - 2 black holes, each around 30 solar masses, rotating about a common centre of mass, 10s of times per second, just before coalescing.

Immediately before & after, the signal is simply not detectable with our current technology.

In the future, we'll be able to detect many of these ultra-energetic, cataclysmic events using multiple GW 'observatories' around the globe.

That will allow ever-more precise triangulation & current predictions are that we'll identify optical correlations.

This is just the beginning....Wow!

Dean

[silv]

yes, in the press conference video Gary provided a link to, I think the bright-eyed, passionate lady answered this question from the audience in the Q&A.

Such a pitty, Q&A was cut short in the video! Does anyone know of a longer version?

[silv]

I was brooding about the question what was really measured when the spikey pattern occurred.

From what I understood, the measurement describes the amount of the 2 laser beams became out of sync and therefor hit the end mirror at different times than the 0-signal-calibration was set to.

So the time had changed it took the beams to travel the given distance , right?
It was not the distance that changed, only the time it took.
That's important to differentiate, I think, because a friend of mine, also a lay person, and also only IT-educated, imagines that the (3-dimensional) space in the tube had been squished and stretched by the GW causing the beam to have to travel, say, 2 cm more than usual.

But it was the time, only the time.
Just like with the atomic clock ticking slower on Earth, right in the trough of the space-time-liquid/fabric, than up in the air on a plane.

Is that correct?

So if this is right, then this also applies to all "light signals" from distant sources: they are affected by all the random GW which were caused by incidents since the dawn of time.

And that means, the light we observe has not travelled at the same "speed" all the way to us.
It often "surfed", meandered on gravitational waves which caused the light to take longer and shorter to get from A to B.

(The absolute speed itself did not change, okay. But the relative speed did.)

And what might this uncertainty implicate?

Maybe, the light we observe is not as old as we thought it is. Because of a huge amount of incidents with GW radiating through the light's path.

Is an observed redshift red-er because the light encountered a few more GW?

If this is so -
and, at the time we on Earth observe the light beams coming in from different directions of the universe,
they will have encountered different GW tides.
then we are looking at "unclean" environments and the calculations we made based on the assumption that the speed of light is a constant, are wrong.

[sjastro]

The interference pattern is in fact caused by a change of distance between the mirrors hence the time of travel of the split laser beam is different.
The speed of light remains unchanged.

A passing gravitational wave gives space a quadrupole or "squashed sphere" symmetry composed of a short and long axis.
When a gravitational wave passes transversely through a distribution of masses in space the quadrupole symmetry results in either pulling the masses apart or pushing them closer together, depending on the orientation of the wave to the masses.
https://en.wikipedia.org/wiki/File:GravitationalWave_PlusPolariza tion.gif

The LIGO interferometer is based on the same principle. The mirror distance orientated in a longitudinal direction to the wave remains unchanged but in the transverse orientation, the mirror distance will change due to the quadrupole symmetry of the wave. Hence the differences in the longitudinal and transverse mirrors distances will be detected as an interference pattern.

[gary]

Hi Sliv,

To provide some sense of how miniscule the changes in distance being
measured are, LIGO can resolve down to 1/1000th the diameter
of a proton, or some 1 x 10-18 meters.

That is 0.00000000000000001 meters.

If you drew a line between the Sun and the next nearest star some 4 light
years away, LIGO could detect the change in distance down to the thickness of
a human hair.

[silv]

Thank you reading and replying :)

What I struggle with is:
are these metaphors used to accommodate the audience's 3-dimensional thinking?

is this only a metaphor:
stating that the mirror moved on its suspension ropes - (let's disregard whether by a fraction of the size of a proton or by 2 cm) - or stating that the actual tubes became longer and shorter.

Or was it in actual fact a change measured in the suspension rope (or whatever it looks like in the Ligo, if it's not a real rope).

Or was it in actual fact the length of the tube that got measured? By holding a ruler at it?


Well, I understood those explanations as metaphors.

And I assume, what got in fact measured was the time difference by which the split beams arrived at their common target.

So the light beams got affected by the GW. Time got affected.

And not the stationary objects like mirrors and tubes.

I think here is really my problem: not knowing when scientists speak in metaphors to make it easier to understand - or when they actually speak "autistically exact".

[Bill.davey]

My simplistic understanding is this.
Gravity waves affect the fabric of space-time. The Gw's lengthened and shortened the tubes, the ground around the tubes, the people, everything. As everything physical is affected nothing physical can be used to measure this change in length.
The one constant in the known universe is the speed of light in a vacuum. It is not affected by gravity waves. Therefore the light was used to measure the change in length of the tubes. Tubes at right angles to each other so that they are affected differently by the GW's passing.

[sjastro]

Silv,

No metaphors are being used as the descriptions are of real events.

General Relativity is counterintuitive because it appears to contradict our understanding of measuring distances.
If the distance between two points changes the logical assumption is to claim one or both points has moved to a different position in space.
Alternatively and far less intuitive is that the two points have not moved but the space between the points has changed.
In this scenario we cannot perceive nor measure the change as a ruler is also affected by the change.

Light however has an interesting property, it will always travel along a null geodesic path. In other words it will always travel along the shortest pathway between two points in space. In flat space this is a straight line, in spherical space along an arc etc.

When a gravitational wave passes through an interferometer the position of the mirrors remain in the same spatial position hence their ruler distance doesn't change.
The geometry of the distorted space between the mirrors is different in the longitudinal and transverse directions.

Light travelling in the longitudinal direction of the wave is on a different geodesic to light travelling in the transverse direction. In the transverse direction the space contracts and expands due to the quadrupole symmetry of the wave. (Expansion occurs perpendicularly to the direction of contraction.)

As a result the two beams will be out of phase and an interference pattern is observed.

Regards

Steven

[Eratosthenes]

the source of the disturbance is non linear and dynamic in nature, and so a "pulse-type" signal is generated.

it is was foreseen in scripture

The great Priest Kip Thorn knew what was coming as far back as the late 1970s......he knew that a LIGO type detector would be built...

He knew that the heavens would open up in rapture

Today we must celebrate the great spiritual achievements of this great global religion - SCIENCE

:D

[Shiraz]

fwiw, the sounds of a few different classes of merger events are here - from 2004, so these are fairly old predictions. http://web.mit.edu/sahughes/www/sounds.html

more up to date stuff with discussion here, but not as easily accessible http://gmunu.mit.edu/sounds/comparable_sounds/comparable_sounds.html

the mergers with a galaxy-class black hole are wild.

[sjastro]

Don't let the facts get in the way of a good story.
https://en.wikipedia.org/wiki/Joseph_Weber

[torsion]

It is an amazing discovery 30-40 years in the making!

Steven in post 36 (http://www.iceinspace.com.au/forum/showpost.php?p=1230741&postcount=36) explains it right.

Some more info:

A nice visual explanation is given here: http://www.phdcomics.com/comics.php?f=1853

A nice public/outreach science summary can be found here: https://www.ligo.caltech.edu/system/media_files/binaries/301/original/detection-science-summary.pdf

An overview of the Australian contribution can be found here: http://www.aciga.org.au/news/australian-contribution

A nice visual and audible youtube clip of the actual event is here: https://www.youtube.com/watch?v=egfBaUdnAyQ&feature=youtu.be

More detailed information (and photos/figures) can be found here: https://www.ligo.caltech.edu/detection

cheers,
Bram

[ZeroID]

OK, so we should expect this then ...

[Eratosthenes]

Surely you are not suggesting that Weber's work was critical to this discovery>? Carving up a bunch of aluminium cylinders that clang together and then calling them Weber Bars just to impress bankers is hardly major progress in this field.

You may owe Kip an apology - he has worked tirelessly over the decades. In fact Kip also looked at the detection of gravitational waves in the 1960s but the technology was not advanced enough at that point in time.

Weber Bars

:D

[torsion]

Weber's work has pushed forward the experimental work on the detection of gravitational waves. His results have been questioned and disputed, but his pursuit for the technological advances were critical. There were many 'bar detectors' around the world, following Weber's work. Much advanced in measurement characterisation has come out of these experiments. So directly, you could say that his work was not critical, but indirectly his work was critical in the pursuit of the detection of gravitational waves.


Rainer Weiss (MIT) was the first who performed a detailed analyses of the inner working of a laser interferometer gravitational wave detector, on which LIGO (and the other interferometers such as Virgo, KAGRA and GEO) are based. Both Kip and Rai (as well as Drever) were instrumental in the development of these instruments over the years.

[Eratosthenes]

...as well as the Russian input on designing and stabilising the 40kg mirrors.

Lots of contributions into these massive projects.

I hope you're not suggesting that just because Eratosthenes invented teh scientific method in ~190BC when he measured the circumference of the earth that HE played a critical role in the detection of the Cosmic background radiation or the positron?

:D

[Shiraz]

Interesting Australian link up - from the MIT LIGO summary.

"Australian groups are also making capital contributions to Advanced LIGO. A consortium of Australian National University and the University of Adelaide are providing Hartmann phase sensors, a pre-lock length stabilization system, and specialized beam-pointing equipment to Advanced LIGO. ANU and Adelaide are full partners in Advanced LIGO."

[sjastro]

You are oblivious to the fact that Weber was the driving force in creating the experimental science behind gravitational waves.

Whereas Einstein described propagating gravitational waves in the arcane mathematical language of time dependent coefficients of the perturbed Lorentz metric, which was cryptic to most people including experimental physicists, Weber showed that if gravitational waves were able to deform an elastic body then it should be possible to drive electromechanical transducers which would provide the signal for the wave's presence.

Your comments on Weber are woefully ignorant and demeaning.

Here is what Kip Thorne had to say about Weber in an excerpt from a Washington Post article after the discovery.


https://www.washingtonpost.com/news/achenblog/wp/2016/02/12/the-many-many-many-unsung-heroes-of-ligo/

[bojan]

~3 solar masses were converted into energy and radiated in the form of gravitational waves.

I am wondering.. if grav energy in form of waves are being emitted, they should be also absorbed, right? Moving and shaking, compressing and stretching masses around..
What effect (on us) would have been if this merger were closer, say in Milky way.. or Magellanic clouds?

If there was a (measurable) effect on light path as consequence of this distant merger, surely the effect would have been very visible if we were closer to the merger?
And how close we should be to see/feel anything?

[gary]

Science Daily on 15th February reports (http://scitechdaily.com/des-results-of-first-search-for-visible-light-associated-with-gravitational-waves/)that the
Dark Energy Survey (http://www.darkenergysurvey.org/index.shtml)used the 3 square-degree, 570-megapixel
Dark Energy Camera (DECam) imager mounted on the
Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory
in Chile to search for any visible light that might be associated with the
black hole merger that LIGO detected.

Working in collaboration with the LIGO team, they began the search within a day
of the gravitational waves being detected.



Article at Science Daily here -
http://scitechdaily.com/des-results-of-first-search-for-visible-light-associated-with-gravitational-waves/

Results in The Astrophysical Journal Letters paper entitled "A DARK ENERGY CAMERA SEARCH FOR AN OPTICAL COUNTERPART TO THE FIRST ADVANCED
LIGO GRAVITATIONAL WAVE EVENT GW150914" by Soares-Santos at. al. here -
http://darkenergysurvey.org/ms-11.pdf

and in The Astrophysical Journal Letters paper entitled "A DARK ENERGY CAMERA SEARCH FOR MISSING SUPERGIANTS IN THE LMC AFTER THE
ADVANCED LIGO GRAVITATIONAL WAVE EVENT GW150914" by Annis et. al. here -
http://darkenergysurvey.org/lmc-paper-v11.pdf

Dark Energy Survey web site here -
http://www.darkenergysurvey.org/index.shtml

[silv]

yes, all sorts of data comparison of before and after the event being measured on Earth! soooo intriguing!

I read about a longterm Pulsar project in which the goal is to detect GW passing by their system by constantly measuring it's pulse and looking for deviations (Pulsar J1909-3744). Their object of interest is 195 light years away somewhere in Taurus.
So, without knowing exactly where the two BH merged, it's still possible that the GW already have passed by the Pulsar, too, and the deviation stayed undetected. Or maybe it will take another 100 light years for the GW to reach J1909. I don't know.

How exciting is the stuff the Pulsar project members can learn about their assumptions and methods, now, that they know they didn't see what they were looking for, even though it was indeed there: marvellous!
(The article I had read bout it was pre-discovery publication so it didn't state anything about them crawling back into the data or anything, yet.)


Or the Ligo teams themselves:
they can try and understand why their two "rulers" measured different amplitudes in the build-up - and only during the merger-moment became quite congruent. >>image (https://www.ligo.caltech.edu/system/avm_image_sqls/binaries/45/page/ligo20160211a.jpg?1455158181)
It could be a tool's problem of one or the other Ligo - or both.
Or it might be a predictable GW behaviour, previously unthought of. Especially in the light of congruent "chirp" in the merging moment. Assuming if there was problem with the tool, the merging moment would not show up as congruent as it was, either.

[silv]

Bojan has an interesting question, I think: how big and how close by would a GW-creating event have to be so humans would feel/see something?

It was the spanish-accent-lady in the press conference (https://www.youtube.com/watch?v=vy5vDtviIz0) (16:45 - 17:45) who explained that the amplitude of the signal tells the approximate distance as mathematically predictable.
That's not answering Bojan's question, of course, but if one of us knew how to draw predictions relating to event distances, the question would be possible to answer here in the forum.

Another point of view as to how the GW event did indeed already have a palpable effect on humans:
by a delay of 5 months after the detected GW on Earth,
our brains use electrochemical energy to discuss the event.

The time difference of 5 months was caused by the particular form of human observation: scientific publishing procedures being the "sense of perception" of the humans in audience.

Of course, that's rather "quantum" :D in this case synonymous with "esoteric".
But it IS an observable effect the GW had on humans.
Could be used to develop formulae to empathically predict socio-energetic reactions. Or whatever. Maybe stuff for a sci-fi novel.
But certainly, the energy we as IIS members put into discussing the September event,
would have a higher strain amplitude than the GW of 1bn ly away. :)

[silv]

oh, this socio-energetic detector... reminds me of the noosphere project. http://noosphere.princeton.edu
So it's not too "quantum" for humans not to have attempted to scientifically measure and experiment with it.
Although the tool used has proven itself to be inadequate, I think.
Like Weber's bar thingy for GW.

[silv]

ah, here is a catalog of computer simulations re GW:
https://www.black-holes.org/waveforms/catalog.php

Finding out how to translate the data of an event run into meaningful visualization should be only a matter of time.

[xelasnave]

Could the wave trigger star formations or other events within any range relatively close to the merger.

[torsion]

Hi Silv,

Both interferometers saw the same 'amplitude' signal. The LIGO interferometers ran at about 1/4 of their design sensitivity, as well as at the lower 'frequency range' they ran even 'more' noisier. So hence only when the merger signal (say amplitude) came above the 'nominal' noise floor of the detectors, they could see the signal. There is a bit more data analyses in there, but that is the basic limit.

If the detectors were much more sensitive in the lower frequency band (<< 1 Hz), then the orbital signal well before the merger event could be seen. This unfortunately, even at design sensitivity, is not going to happen with LIGO anytime soon..

As for the Pulsar Timing Array, that is a very interesting results. According to the models, they should have seen something and they didn't. So that says something about the models, which in turn is very interesting.

[torsion]

Thanks Gary, hadn't seen those!

Looks like they initially didn't know that it was a binary black hole system, as they anticipated it would be a binary system with a neutron star. I wouldn't think a BBH would have emitted anything, but then that is the unknown we want to see.

[sjastro]

Gravitational waves unlike electromagnetic waves hardly interact with matter.
Gravitational waves act like a mass spring damper system where the amplitude and energy decay over time.
By the time GW150914 reached us only a minute amount of the original energy and amplitude remained.

Not sure of the effects of a gravitational wave originating from the distance of the LMC but nearby you would be flattened in one direction and streched out in the perpendicular direction.

[bojan]

Steven,
thank you for the reply..

From it I gather that in the interaction between mass and gravitational wave, no energy is absorbed (unlike in case of EM waves)?

I would expect something like tidal effects due to gravitational field gradients that propagate through space/time.
Was that way of thinking in the core of Weber's idea (GW prompting the metal cilinder to vibrate at mechanical resonant frequency and picking those vibrations with piesoelectric sensors)?

[Shiraz]

this is a bit old, but may be useful summary of gravitational wave energy? http://ned.ipac.caltech.edu/level5/ESSAYS/Boughn/boughn.html
It seems to be an exceptionally inefficient way to transfer energy and only viable when the source is capable of generating vast amounts of energy in a short time - such as the black hole merger where 3 solar masses were converted to GWs in a fraction of a second.

[bojan]

Ray,
I had in mind exactly what this article describes when posting my question.

Appropriate (very small.. the factor is 1e-43, compared to EM interaction with electrons) part of energy carried by GW must be absorbed by mass .. and possibly dissipated within the receptor as heat. Similar/analogous to EM.

Now, we have here 3 solar masses converted into GW energy.. this is a lot of energy and this must interact noticeably with nearby objects... it would be interesting to put that into our everyday perspective.

I found more on power radiated by oscillating masses here:
https://en.wikipedia.org/wiki/Gravitational_wave
http://sciencejedi.com/professional/classes/astrophysics/lectures/lec09_gw.pdf
http://gizmodo.com/your-questions-about-gravitational-waves-answered-1758269933

"How far away do you have to be from this kind of black hole merger to live to tell the tale?
Stuver: For the black hole binary we detected with gravitational waves, they produced a maximum change in the length of our 4 km (~2.5 mi) long arms [of] 1x10-18 meters (that is 1/1000 the diameter of a proton). We also estimate that these black holes were 1.3 billion light-years away.
Now assume that we are 2 m (~6.5 ft) tall and floating outside the black holes at a distance equal to the Earth’s distance to the Sun. I estimate that you would feel alternately squished and stretched by about 165 nm (your height changes by more than this through the course of the day due to your vertebrae compressing while you are upright). This is more than survivable."

The above quotation summarizes the issue of noticeability.. provided the calculation involved was correct.

[sjastro]

Strictly speaking it is not a tidal effect. The stretching and compression associated with a tidal effect is due to the action of a gravitational force acting in one direction. In a gravitational wave there are two "distinct forces" acting perpendicular to each other.

Weber was able rewrite the motion of test particles effected by gravitational waves using a model where a volume of space time is occupied with a elastic medium.
The medium is subject to deformation by the GW and in theory be detectable with piezoelectric sensors.

His ground breaking paper is here.
http://journals.aps.org/pr/abstract/10.1103/PhysRev.117.306

Unfortunately there is a paywall.

Regards

Steven

[Eratosthenes]

interesting notion. Waves have valleys and peaks and points of inflection. One would assume that any nearby dust and gas will be effected in various ways. Gathered and carried along perhaps? Concentrated into the seeds of future stellar or galactic structures??

I recall reading that the two black holes that are spinning around one another are 29 and 36 solar masses. When they combine they will produce one black hole with an estimate mass of 62 solar masses.

There are 3 solar masses which are channeled elsewhere - will most of this massive energy end up powering the gravitational wave?

In any case these pulses of Hades are supremely powerful, especially close to the source.

I would like to see another LIGO type detector constructed - preferably in Australia with evacuated tubes over 100km long and arranged in a Crucifix geometry.

:D

[xelasnave]

I thought if we looked past the merged black hole (behind it) we may be able to observe close stars say one light year "respond" to the passing wave. Looking behind may show something. The event was say 1.3 billion light years so if we observe something 1.3 billion light years plus one light year next September we maybe see it pass by that object.
But I see new links that I must read.

[Eratosthenes]

one year later in a 1.3 billion year time frame is a very small percentage ~0.0000000769 %

What do you expect to extract and delineate from a measurement in September 2016?

The signal was already very faint in September 2015 - and that signal was most likely the peak of the wave - ie one of the initial wave pulses

Unless some sort of pre-event has been measured and there is something bigger yet to reach us.?

:D

[xelasnave]

I have no idea of the possible effect.
Say there is a star or other object one light year past our event if there is anything to observe we could make the observation next September.If there was an object close behind we would see that event after last September.

[xelasnave]

the percentage is irrelevant but it may be we could observe effects behind which will not reach us until a future time.

[bojan]

Alex,
have a look at the link below to get some feeling about what the effect of the GW source in question is on "distant" object:
http://gizmodo.com/your-questions-ab...red-1758269933 (http://gizmodo.com/your-questions-about-gravitational-waves-answered-1758269933)

I was surprised myself when I've read it.

"How far away do you have to be from this kind of black hole merger to live to tell the tale?
Stuver: For the black hole binary we detected with gravitational waves, they produced a maximum change in the length of our 4 km (~2.5 mi) long arms [of] 1x10-18 meters (that is 1/1000 the diameter of a proton). We also estimate that these black holes were 1.3 billion light-years away.
Now assume that we are 2 m (~6.5 ft) tall and floating outside the black holes at a distance equal to the Earth’s distance to the Sun. I estimate that you would feel alternately squished and stretched by about 165 nm (your height changes by more than this through the course of the day due to your vertebrae compressing while you are upright). This is more than survivable."

The above quotation summarizes the issue of noticeability.. provided the calculation involved was correct.

[xelasnave]

Thank Bojan.
That's cleared it up for me.
Surprising indeed.

[torsion]

Hi bojan,

As for the interaction to measure the gravitational wave, because gravitational waves have such a weak coupling with matter, that is what made the measurement so incredible difficult.

Weber's principle idea was that the gravitational wave would 'ping' one of the resonant modes of the bar, and then he would readout the 'energy/displacement' of that resonance. That made these bar detectors 'resonant bar detectors', looking at gravitational waves around 1000 Hz (actual frequency depends on the resonant mode of the bar). The signal could be followed for maybe 10 Hz to 20 Hz, and then disappeared in the noise.

The LIGO detectors, are 'broadband' detectors, and are able to follow the gravitational wave from 10 Hz to 8000 Hz. The GW150914 event was a signal from 35 Hz to 150 Hz, over a period of 0.2 seconds.

As for more detectors, they are coming online (Virgo early next year and KAGRA later), just takes time:( I am all for a detector in Australia... would be nice. That would primarily help with the sky localisation for EM followups.

Also, LIGO made an initial faq page which may be of interest, https://www.ligo.caltech.edu/page/faq

[Eratosthenes]

I am astonished that the LIGO group used flimsy 40kg mirrors in the detector. This decision alone almost destroyed any chance of a successful and meaningful measurement....

These yahoos were lucky this time - thanks to the Russian researchers in Moscow who covered the LIGO group's backside...just to save on some glass costs - absolutely ridiculous.

:D

[julianh72]

Unless I am misunderstanding the situation (which is entirely possible; probable even!), I'm not surprised that we didn't see a corresponding change in the Pulsar timing yet.

The gravitational waves reached us by travelling in a straight path 1.3 billion light years long (if "straight" means anything when we are talking about distortions of space itself!). Unless the pulsar we are monitoring happens to lie on the same "straight" path (VERY unlikely!), the path length from the Black Hole Merger to the Pulsar to Earth is longer than the "straight" path from the Black Hole Merger to Earth.

If the Pulsar happens to lie close to the straight path, between Earth and the merged Black Holes, it would have felt the gravitational waves before us, but as the cumulative path length is longer, the disruption to the regular pulsar frequency won't reach us for some time yet. If the Pulsar lies 100 light years beyond us, the gravitational waves won't reach it for another 100 years, and then it will take another 100 years for the Pulsar fluctuation signal to reach us.

[Shiraz]

I think that the pulsar study is based on a totally different timeframe (eg cycles per year, not 100 Hz). The pulsar study is looking for long slow galaxy-class events, not small black hole or neutron star mergers - from my limited understanding, the zippy merger that was observed with LIGO would not register on the pulsar study.

For interest, it seems that Australia could possibly have had a LIGO, but the Government was not able to finance it. From Wiki, "The LIGO-Australia plan was approved by LIGO's US funding agency, the National Science Foundation, contingent on the understanding that it involved no increase in LIGO's total budget. The cost of building, operating and staffing the interferometer would have rested entirely with the Australian government.[6] After a year-long effort, the LIGO Laboratory reluctantly acknowledged that the proposed relocation of an Advanced LIGO detector to Australia was not to occur. The Australian government had committed itself to a balanced budget and this precluded any new starts in science. The deadline for a response from Australia passed on 1 October 2011." https://en.wikipedia.org/wiki/AIGO

[sjastro]

To expand on Ray's post.

Gravitational waves are emitted in all directions and continuously up to the time of the Black Hole merger.

The Pulsar timing array is designed to measure fluctuations in pulsar arrival times caused by gravitational waves which alter the Earth-Pulsar distance.
The Pulsar fluctuation times are long period events, and are expected to be caused by gravitational waves of very low frequency (long period).
These very low frequency gravitational waves are generated by orbiting supermassive black hole binaries in galaxies.

GW150914 on the other hand is an example of a Black Hole merger producing gravitational waves in the high frequency range which would not impact on pulsar fluctuation time.

http://nanograv.org/assets/img/GWBigPicture.png

Regards

Steven

[silv]

I just >>read (https://theconversation.com/where-are-the-missing-gravitational-waves-47940) (in the comment section) that the Pulsar Timing Array is looking for a different kind/source of GW: higher amplitudes but much much lower in frequency. Like from binary supermassive BH within 2 merging galaxies.
Ligo is not designed to detect those kind of waves and vice versa.
>>abstract (http://arxiv.org/abs/1509.07320)

Binary supermassive black holes - that's also the subject of observation of the future eLISA in 2035, with a laser beam length of 1 million km. Well, sexy, but... that's kind of too much in the future for my attention span.
A mission for an eLisa instrument test, "Lisa Pathfinder", is going to go into science mode on March 1st.
Here, the laser beam is shortened to 38cm to fit into 1 spacecraft.
The test is about gaining info on the "rulers'" functionality and exactness in a free fall environment, which can not be obtained on Earth.
I would follow the mission or eLISA on Facebook. Only to keep being reminded of - and through that, possibly commit into long term memory what I understood so far.
But they don't have their own page. Just not sexy enough...
Ah well.

[xelasnave]

Lets build a bigger better one and rent it out?

[Eratosthenes]

definitely the way to go...

but this time don't skimp on the glass in the mirrors

the clowns in the LIGO group got away with it this time, with the help of a few Russian geniuses in Moscow.

Aussie mirrors should be at least an order of magnitude heavier - at least 300kg, bare minimum anyway.

We have lots of sand on our coastline so I really dont see what the problem is...

:D

[xelasnave]

Why have large mirrors we may need to move it.
One inspace maybe?

[torsion]

Hi Julian,

Sorry didn't see you post, but a few have answered your point nicely.

In the Pulsar Timing Array, they use the pulsars and earth as 'the test masses' to measure the timing, while in LIGO they use the 40 kg test masses 4km apart to measure the timing.

The test masses (four of them in total per interferometer), are about 34 cm in diameter and 20 cm thick, made of low-mechanical-loss, high quality Fused Silica. They have been polished to have a concave surface on the front with a radius of about 2 km (and flat on the back). Then they are coated with high quality, low-optical-loss coatings (high reflectivity on the front and anti-reflective on the back). They are manufactured in a joined effort in the US, UK and France, with reference measurements done at CSIRO - Centre for Precision Optics (if I am not mistaken).

The concave polishing and the coatings are required to form a stable, low loss optical Fabry-Perot cavity. Any loss will remove photons which are then not used in the sensing of the signal. Also, additional loss can turn into heat, which will deform the mirrors, and introduce loss. Hence they use the low-loss materials to reduce all this.

The 40 kg is a ~4x increase in mass from the original LIGO detectors. The difficulty is homogeneous polishing and coating of the 34 cm diameter, which was quite a challenge. Any ripples etc on the mirror surface will introduce loss. Going to much larger mirrors makes the manufactory of them impossible (currently). You can think of a compound mirror (made of multiple pieces), but then any loss near the joining faces will/can increase the noise.

A nice photo of one of the Advanced LIGO mirrors is here http://www.ligo.org/multimedia/gallery/opt-images/7442_20130617072621_BSC1_130606_13-29-56_mod_llo_itmy.jpg. The wiggles on the mirror are from a special protective coating, which will be removed when work is done nearby. (more photos here http://www.ligo.org/multimedia/gallery/opt.php)

[Eratosthenes]

At least the vacuum bit of the design is already up there....great thinking xelas

How do we get the 600kg mirrors up there though?

Do you know if there Are deposits of sand on Pluto or Europa?

May need to crunch the numbers before we float the idea on Wall Street.

The fascist bankers on Wall Street are very picky and would want some short term returns, one would think.

:D

[xelasnave]

No mirrors just a transmitter beam splitter and receivers.

The bankers can make money short selling shares in mirror companies as sucess of the mirror less system will see them plumet.

Look I dont work on the trivial aspects of the plan I just come up with magnificent ideas it is up to the staff to iron out perceived difficulties and make my ideas work.

[Eratosthenes]

I dont think the good folk of iceinspace have ever doubted that Universal axiom xelas

having said that however I will say this...."it's critical that you at least help out with the nitty gritty of the Space LIGO project - especially the mirrors even if they arent really required. I am a strong believer that mirrors should be installed in the next generation of LIGO detectors irrespective of whether they are part of the measurement or not. Heavy mirrors. massive heavy mirrors - at least 15 of them weighing over 900kg each - The mirror system will impress investors and bankers to fund the project in space".

You may wish to consider consulting with an expert who is commercially savvy and understands the criminal system that underpins Wall street and the casino stock market before you stampede towards getting your little idea off the ground.

:D

[xelasnave]

Of course all recognise my magnificence but there is little point in restating the obvious. AS humble as I am I find continual praise unnecessary please praise the wonderful ideas not the man as it is conceivable that others may also have reasonably good ideas.

You seem to sence what I expect and have knowledge of financing so just get things moving and advise my secretary the openning date so she can get my tux pressed. But make sure you order two of everything... In time you will appreciate why I follow such a policy.

Please insist my name does not appear anywhere unless of course you negotiate a suitable fee (contact my agent and he will go over my rates) if you feel my endorsement is critical to further funding.

And perhaps drop your referrence to Greece and their scientists, the bankers may become worried that the project may be financially dubious.

So any more on the recent news the subject of this wonderful thread.

[Eratosthenes]

Greece is not what it appears in the media.

About 30% of the worlds shipping vessels are under Greek Control (that figure was over half when Onassis and the other Shipping magnates were running the ocean circus)

We seem to have some supreme characteristics in common xelas.

Dont tell me that you are sublimely handsome and creatively gifted as well?

These gifts can be a curse though - woman just cant get enough

In the early 1990s I need to resort to an office with three secretaries so that I can handle the bookings and social revenue flows.

Anyway, you were very cunning to divert the conversation away from the 900kg mirrors and into other trivial areas.

You may be able to get away with that childish ploy with other posters in here but not here - no Siree bob.

you may need to apologise in order to move forward from this

Good luck

[xelasnave]

I am very good doing appologies because I am humble.
I am sorry for any offence you may perceive I am guilty of.
I am happy to have mirrors just order double.

[Eratosthenes]

You should only apologise if you dont mean it and your apology pertains to the mirrors only.

You would never see me apologising for non-mirror related infractions. Never.

You do know what xelas means in Greek dont you xelas?

:D

[xelasnave]

never say never and never twice.

[torsion]

Other exciting news is that the construction and building of a third LIGO detector in India has been given the go-ahead (http://indianexpress.com/article/india/india-news-india/union-cabinet-clears-ligo-india-gravitational-wave-observatory/). This project, LIGO-India (http://gw-indigo.org/tiki-index.php?page=LIGO-India), will be part of the array of US LIGO detectors.

This will greatly help improve the sky localisation of the source of the detected gravitational waves. The GW150914 event was localised in to a 600 deg^2 sky area. This made is very difficult for the EM followup telescopes, most with with small FOV, to find anything. The Dark Energy Survey, mentioned before, is one of these telescopes doing EM followups.

Combining EM followup with the gravitational wave detectors will be the next phase in GW astronomy.

[Shiraz]

for $140m it could have been in Aus. :(http://www.aigo.org.au/aigo_web_docs/LIGO-AustraliaProposal.pdf

[Eratosthenes]

Australia prefers to use almost 12 billion dollars EACH YEAR of Tax payers money to subsidise and help out the 83% foreign owned fossil fuel and mining industry which only employs about 3% of the Australian workforce and which doesnt pay very much tax.

Australia also prefers to have one of the worlds most lucrative negative gearing tax evasions schemes in the world, which costs the Australian tax pay many billions of dollars in tax revenue each year.

Australia also prefers to spend about 2.5 billion dollars per year detaining refugees in off shore detention centers - a cost which equates to almost $180,000 per refugee per year. All of these costs are met by the Australian tax payer and end up as profits for private individuals and corporations (most of which are foreign owned).

There is no way known that Australia could think big and fund such a project. No way Jose. India can, but there is absolutely no way Australia can - no way!!!

:D

[sjastro]

A follow up Bojan's post

The effects of gravitational waves on us if the source was closer.
In summary we would have to more to worry about the effects of black hole tidal forces than the GWs themselves.

https://briankoberlein.com/2016/02/19/how-close-is-too-close/

[Eratosthenes]

...yes Bruce, we wouldn't want any of our cells or molecules in our supremely stationary bodies, suddenly moving a fraction of the diameter of a proton now would we ladies and gentlemen.

We definitely need the world authorities to construct anti-GW devices to compensate for these unforeseen perturbational effects in the space time continuum - the very fabric of space-time - the nylon of our innate existence, the underpinning tarpaulin of existential transformation in the chronologically tempered space membrane

..... just in case something happens.

:D

[bojan]

Interesting...

Do we have estimation how much energy was converted into GW since BB?
It may be a significant amount, and was "lost" ... except for gravitational effects (it become part of dark matter).

[sjastro]

The short answer is we don't know.

A major source of GWs should theoretically originate from the inflation stage of the Universe some 10^-36 sec after the BB.
Unlike the initial high frequency of GW150914 which was detected by LIGO, these extremely low frequency primordial GWs can only be indirectly detected by measuring a particular type of polarization of the CMB (Cosmic Microwave Background).

Unfortunately in one of the great "stuff ups" of modern cosmology the observed polarization can also be caused by photons from the CMB reflecting off magnetized dust in our own galaxy.
Scientists underestimated this phenomena in making a premature announcement of the discovery of GWs from the inflation period.

http://physicsworld.com/cws/article/news/2015/feb/03/galactic-dust-sounds-death-knell-for-bicep2-gravitational-wave-claim

Since these GWs are masked by local effects, we don't know how much energy has been carried away by GWs since the BB.

[Atmos]

Dark Energy!!! Albeit silly, it remains a valid claim until someone proves me wrong ;)

On a more serious note, I have been trying to visualise the gravitational wave from the BB in my head. Not the most "sciencey" approach but I would imagine that the gravitational wave would be long and low amplitude to the point that it may just be a permanent background noise without any detectable wave form.

We are still a LONG way from having that kind of resolution in gravitational wave detectors. Luckily, we only really need one detector for it because it is everywhere so we don't need to pinpoint a location :)

[gary]

"High-energy Neutrino follow-up search of Gravitational Wave Event GW150914 with ANTARES and IceCube" submitted to arXiv 17 Feb 2016 by S. Adrián-Martínez et. al.



Paper in PDF here -
http://arxiv.org/pdf/1602.05411v1.pdf

[torsion]

That would assume there is a uniform distribution. That would the the stochastic background radiation, which I think doesn't need to be uniform. But I guess that is 'frequency' dependent (e.g. LIGO band, PTA band etc).

[sjastro]

Visualizing how a gravitational wave of any amplitude or frequency impacts on space time is a difficult exercise given the wave only acts transversely on particles in space-time.
Then there is the complication with polarization. Gravitational waves like electromagnetic waves can be elliptically polarized.

Here is what a simple gravitational wave looks like.
http://www.einstein-online.info/spotlights/gw_waves/?searchterm=gravitational%20waves

[silv]

India. What a pity.
They have so many earth quakes there that it must be like an annoying tinnitus - having to substract the rumbling from the stabilization and graphs.
Australia would be so much easier to maintain.
Or is the location favorable as third Ligo for triangularisation?

In light of earth quakes - I wonder what marvels the Japanese installation has to develop to cancel out those influences. And how those developments might be adaptable outside of interferometer applications.

[silv]

but there are different forms of "interactions". and one of them is predicted to take energy away from the GW: meeting up with oscillation of light.
when GW pass by a star and the two waves meet - and IF the frequencies are favorable to react in such a way:

the light of the star should appear to brighten.

[Eratosthenes]

what is "lost " energy?

[sjastro]

Energy loss from a GW occurs on local and cosmological scales.

On a local scale a GW loses energy by doing work on stretching and compressing objects (ie LIGO, people, particles distributed in space etc).
GWs however do not directly interact with matter like photons in scattering and absorption/emission processes.

On a cosmological scale, GWs like photons, lose energy through cosmological redshift.

Steven

[Eratosthenes]

energy can NEVER be lost

NEVER!

:D

[sjastro]

You are displaying an ignorance of General Relativity.

The conservation of energy is a Newtonian concept based on static space-time at non cosmological scales where objects move in space-time rather than carried along by space-time such as the recession velocity of galaxies.
In fact the recession velocity vs distance of galaxies even before the discovery of dark energy might have provided you with a valuable clue the conservation laws don't apply.
When space time is not static such as an expanding Universe or the passage of a gravitational wave, General Relativity is used.

Where as energy is conserved in Newtonian physics, energy-momentum is not necessarily conserved in General Relativity.
This has been known since the 1920s but requires a knowledge of tensor calculus in order to be understood.
In laymans terms if space time is not static the conservation of energy is not applicable.

Another obvious example is the cosmological redshift of photons.
This is an energy loss. Where do you think the energy goes?
Similarly GWs undergo energy loss at cosmological scales due to redshift.
At local scales GW energy loss is due to the work done on expanding/compressing matter.

[Eratosthenes]

Bruce fails to comprehend the basics of thermodynamical principals and applies pseudo logical rationale to make a misinterpreted point concerning General Relativity....

and easy error to make, and often found in secondary school Physics classes

nevertheless it must be exposed as quackery in public in the name of science, truth, justice and the American way

:D

Just because the equivalence of the integral form of “energy conservation” in relativistic FLAT SPACETIME breaks down when one tries to generalise it to curved spacetimes (ie General Relativity) doesnt imply that the laws of conservation of mass and energy have been violated. This break down does not occur if one expresses the energy conservation as a differential equation. (perhaps Bruce can explain that mathematical lunacy)
There are of course definitions of “energy” in GR that relates to a closed universe – a Hamiltonian – and this energy nicely and always works out to be ZERO.

In the end it depends on how one defines "energy" and how one defines "conservation" - even Bruce would understand and concede this elementary linguistic imperative

Definitions, definitions and assumptions…..we can all hide our ignorance and intellectual patheticness behind these…

a couple of excellent references for this sort of deranged Physics:

The renaissance of general relativity, in The New Physics (ed. Paul Davies) Clifford Will.

Seventeen Simple Lectures on General Relativity Theory Lecture 15 H. A. Buchdahl, (derives the energy-loss formula for the binary star, and criticizes the derivation)

classic Buchdahl, demonstrates the derivation and then critically dismantles its very essence - pity there arent many Scientists in the world today like Buchdahl - we mostly have puppets and circus clowns - scientific priests that read from their religious and dogmatic scriptures whilst wearing their pathetic lab coats and collecting their corporately owned state pay cheques.

[Shiraz]

thanks very much for the insight - I hadn't taken this on board, even though I was well aware that redshift reduces photon energy (it never occurred to me to ask where it went):P.

I found this blog by a CalTech physicist that is clear enough for me to understand. http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/

[sjastro]

Your quote reminds of me of Benjamin Franklin's famous quote.


It is an exercise in word salad to create the impression of comprehension.

Its quite comical for you to invoke thermodynamics as a reason why energy cannot be lost because an effective argument as to why an expanding Universe does lose energy without going through the complications of GR is to use the first law of thermodynamics. :rofl:

The first law states the energy change (dE) of a system is equal to the heat energy change minus the energy done by work on or by the system (-PdV).
dE = dQ -PdV

Where a system is the observable Universe, heat energy is conserved hence dQ=0.
Ignoring the presence of dark energy, photon pressure (P) in the Universe is positive and given the Universe expands dV increases and is always positive.
Hence dE is negative and indicates energy is being lost.



Who are you trying to kid?
Given you are incapable of understanding the energy loss using a very simple thermodynamic argument, you are now trying to con your way by selectively cutting and pasting comments with some minor editing from this link.
http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html

It is dishonest to cherry pick selected passages given in the article.
All you have done is to fish around for various sentences that might have some vague connections to your prejudices. Strange how you have ignored the references to static Universe.....
It illustrates the article is way beyond your comprehension



Cutting and pasting two of thirteen references from the link and "claiming" you are familiar with the works is highly suspicious.
Its up to you to show you are in fact familiar with Buchdahl and not just engaging in blatant lying.

There is no link I can find about Buchdahl's work, only a book is available.
Why don't you supply a scan of the book's cover since you have "obviously" read it.

[sjastro]

Thanks for the link Ray.
Sean Carroll gives an excellent description.

Regards

Steven

[Eden]

Things did not end well for Ken Ham when he tried this on Bill Nye...

[Eratosthenes]

So now you are doubting the great Buchdahl - a person of high respectability in the scientific community - and in particular the teaching of complex concepts to eager

I really cannot see how the citation of first year Thermodynamic principles and false Gibbs free energy equations will assist the superstition based sorcery that you are pedaling in here.

Its clear at least, that you owe xelas and Buchdahl a written apology.

:D

[Eratosthenes]

so true Brett

but it appears, at least for some in this forum, that basic logic and common sense are not noble pursuits

:D

[sjastro]

I can see how much you have been keeping up to date on the guy's work particularly his teaching to the eager.
Unfortunately he has been dead for over six years. He must teach via a medium.
I'll need the medium to apologize to him. At the same time I'll request his book "Seventeen Simple Lectures on General Relativity" for you as it is blindingly obvious you have absolutely no idea about his works.



Gibbs Free Energy is dG= dH- TdS.
Even someone who knows absolutely nothing about thermodynamics a casual glance between this equation and the first law dE = dQ -PdV indicates they are completely different.
The Gibbs free energy indicates whether a process such as a chemical reaction is favourable or not, or is in equilibrium.

Its ironical that ignorant people who try to hide their ignorance by throwing in "big" terms, like Gibbs free energy in this case, only make themselves look more ridiculous in the process.

Since you know more than any cosmologist or mathematician on the subject explain where the does the energy go when a photon undergoes cosmological redshift.
Better still contact the cosmologist Sean Carroll and refute his webpage.
http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/

[Eratosthenes]

diversions will not assist you now.

All you have left is your ethical and moral responsibilities and your apology which is in arrears. And it must be unconditional and in writing.

:D

(did you actually read my post? I said FAKE Gibbs Free energy - and just like clock work you fell into my little religious trap - You fundamentalist priests are all the same)

[multiweb]

:eyepop::lol: Well... that thread turned to sh!t... what have you started Gary? :P

[xelasnave]

No. Steven it putting up good stuff.

[Eratosthenes]

what about Bruce?

The religion of science is holding strong even though its fundamentalist dogmatism is so fragile

:D

[Shiraz]

yes, that was a pity eh!

Started out quite coherently as an expression of genuine excitement at a momentous scientific discovery and then got dragged down Alice's rabbit hole...Some really good information penetrated the haze though.

[Eratosthenes]

I am still trying to find out how someone can provide an equation to the FAKE Gibbs Free Energy, which apparently doesnt exist in this Universe, and then compare it directly to the first law of thermodynamics.

Perhaps there is a religious explanation to this incredible online analysis?

:D

[bojan]

Pardon my ignorance, but.. who is Bruce?

[xelasnave]

Peter is playing the fool, there is no bruce.
He is trolling Steven and in an effort to insult Steven he seems to think calling him bruce is funny. It is insulting and poor behaviour from Peter. Probably breaches the tos
Peter has some sort of chip on his shoulder relating to science and scientists and he no doubt views Steven as fair game.

Given his rants I suggest he wants to divert attention away from the op.

The positive is although this site is relatively free of crank behaviour peter is here to remind us how tiresome crank behaviour is and how clever he is engaging in a battle of witts completely unarmed.

His rants need to be ignored as it is clear he is not interested in being decent.

Presumably peter has his reasons which hopefully he wont share with us.

I would encourage members to ignore peters rants for in time he may regret acting the fool...

[bojan]

I've got that part a long time ago...

[Eden]

Very unlikely. In future, please consider conserving your own energy.

[multiweb]

Steven knows his stuff and has always had something valid to contribute. Just referring to the other background noise. :)

[Shiraz]

as was I:thumbsup:

[gary]

IIS member Robert9 has just made a post in General Chat which includes a link
to a YouTube video recording of a seminar at Monash University
by Associate Professor Yuri Levin and Dr Eric Thrane of Monash University
who were part of the LIGO team -

Post here -
http://www.iceinspace.com.au/forum/showpost.php?p=1232899&postcount=32

Thanks again to Robert9.

[Eratosthenes]

excellent summary xelas (even though you neglected to mention one very important point)

:D

[Shiraz]

it looks like they could possibly have seen more than one event in the data period, even though the next most likely candidate is only at 2sigma. This could be an exciting year!! :thumbsup:

http://physicsworld.com/cws/article/news/2016/feb/15/new-insights-emerge-from-ligo-gravitational-wave-data

[Somnium]

2 sigma ... meh :)

[Shiraz]

:rofl:

I am about 95% confident that, had they not found a 5sigma event, the 2sigma one would have been splashed all over the media - provided of course that it is not an injected test signal.

[Somnium]

i would hope they wouldn't splash a 2 sigma detection around, that just means that out of 20 candidate signals they would give a false positive reading on 1. mind you i have no idea how many candidate signals they look at but 2 sigma is way too low

[Shiraz]

sure its is too low to qualify as a detection under the 5 sigma rule that the particle physicists have embraced. However, if you are 95% confident that you have found something, you cannot ignore it either. The particle physicists would just plough on with more runs until they had more confidence, but that is not an option with a strictly one-off gravitational wave detection. I would think that co-incident 2 sigma events at each of the two detectors would have to be quite significant - although who knows how they assess confidence when they are looking for something from a group of "sort of predictable" structured signals, at 2 sites and against noise that presumably has both random and structured components.

Let's see what they do, but it is interesting that that have already begun to publicise the extra candidate events, even those below 2sigma. My guess is that, now they have one hard detection and a lot of real noise to study, they will be able to increase the confidence estimates on any other candidate events.

[Shiraz]

The paper itself - I don't think this has been linked to elsewhere in the thread?
http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102

[sjastro]

Interestingly enough the neutrinos travelling faster than light fiasco was a six sigma event but with no confirmation test on different apparatus.
History has shown it was a nice strong signal of a systematic error.

Dark matter has been "detected" at three sigma using the SuperCDMS but the calculated mass/collision cross section are inconsistent with the exclusion limits of the Xenon10 and 100 detectors.
http://www.science20.com/science_20/wimp_3_sigma_signal_road_dark_matte r-109299

Steven

[Dave2042]

Good points. I have always felt that there is a danger of missing the wood for the trees in discussions of statistical significance and sigmas.

The reasons, as I see it, that sigma is so critical in particle physics are:


It is generally not known what is 'expected', or predicted by an accepted theory. Indeed, whether the 'blip' is real, is a driver of whether we like one theory over another, given the endless variants of possible theory.
You can simply do more runs and drive sigma up as high as you like, or to zero, and settle the matter.


This is not like that.

We strongly expect gravitational radiation to exist, for widely accepted theoretical reasons, as well as having the second 'simultaneous' signal telling us this is not just a glitch.
We can't just do more runs. This is what we have and we need to work with it.


This is more than just an appeal to Bayesian stats. My point is a more fundamental one about what sigma is. All it tells you is something about the likelihood the signal could have been generated randomly. This number operates in total blindness to any theoretical background or extraneous but relevant information. That's kind of fair in much of modern particle physics, but certainly not here.

The worst (but I feel clearest) example of this misunderstanding is the one where we look at climate stats and say that the probability of the rising temperature data being random is 5%, and conclude there is only a 95% chance we are causing global warming. In fact we know (in the usual sense of the word) that it's warming and we are doing it, from basic science. The uncertainty exists only in relation to our ability to measure the current effect above a lot of background noise.

[bojan]

For those who want to understand more about GW... but in a more simple terms:
http://www.tapir.caltech.edu/~teviet/Waves/index.html

[Eratosthenes]

good post. It's rare to find scientific articles (especially those based upon experimental investigation) that include the three main sources of errors - Systematic, statistical and theoretical i.e Graphs with data points that show 3 error bars.
And there is the common confusion between what is meant by precision and what is meant by accuracy.

I recall attending a session at a seminar/conference some years back where the author presented a graph with only 3 data points and no error bars included. He then fitted some sort of parabolic curve to these 3 points, and extracted a value for a maximum. I asked him how he chose the type of curve and what the regression coefficient was with just 3 data points. He answered by saying that each data point involves about 2 months work, and that he knew from other research that the relationship was non-linear. ;)

One can fit just about any curve to 3 points. It would be like claiming a linear relationship with just two data points.

If you look at the original Hubble data you can see a general upward trend, but the scatter in the data was large and the galaxies that were observed at the time, with the equipment and techniques available, were nearby or very large galaxies. A linear relationship was nevertheless fitted by Hubble and a value for the Hubble constant extracted. It took many decades to obtain data from distant galaxies that showed the Universe was not only expanding but that this expansion was accelerating.

Error bars from all sources, and their justification is very important in the scientific profession and normally taken for granted

:D

[Eden]

Definitely worth a read. I wonder how long it will be before ALIGO is up and running and making regular detections?

[gary]

In a February 23rd press release (https://www.cfa.harvard.edu/news/2016-05) by the Harvard-Smithsonian Center
for Astrophysics (CfA), they report that the Fermi Space Telescope
detected a gamma-ray burst just a fraction of a second after LIGO's.





Press release here -
https://www.cfa.harvard.edu/news/2016-05

"Electromagnetic Counterparts to Black Hole Mergers Detected by LIGO" by Loeb, full paper in PDF at arXiv -
http://arxiv.org/pdf/1602.04735v2.pdf

[Shiraz]

but the equivalent European GR satellite did not see anything at all and it was in a position to view the whole region of the LIGO detection.
http://phys.org/news/2016-02-gamma-ray-accompany-ligo-gravity.html
http://arxiv.org/pdf/1602.04180v1.pdf

the following is from the author of the paper dealing with the possible structure of a star with a pair of black holes at it's core: "Even if the Fermi detection is a false alarm, future LIGO events should be monitored for accompanying light irrespective of whether they originate from black hole mergers. Nature can always surprise us," says Loeb.

it's all happening :)

[Atmos]

There is always a possibility that there will not be any detectable GRB or neutrino fallout with a black hole merger. Certain Type II sn are neutron star-neutron star or neutron star-black hole mergers but in cases there is at least one object that has material outside of the event horizon radius :)

[sjastro]

An interesting story.

The reviewer of Einstein's paper was Percy Robertson a "co father" of the Big Bang Theory.

http://www.astronomy.com/news/2016/02/even-einstein-had-his-doubts-about-gravitational-waves

[Eratosthenes]

Q.3 What is "happening" at the point of contact and subsequent merging of the event horizons in the case of two black holes colliding and forming a single black hole? How do we geometrically and mathematically describe the event horizons of the two black holes as they touch and combine? Do special contact and intersection points form? If so, what happens at these points

[25 marks]

:D

[Atmos]

For the answer to that I deserve a Nobel Prize :lol:

[Eratosthenes]

I cant alter the [25 marks] for this particular question. It wouldnt be fair on all the other students who are sitting the exam.

Its interesting to note that the September 2015 measurement at the LIGO facility, occurred a few days prior to the official opening and whilst it was undergoing some tests before the ceremonial opening.

The LIGO researchers were working hard to meet the deadline and when they left the facility at 2:00AM in the morning, they decided to leave the detector on. The GW blimp decided to hit the earth a few hours later at about 4:50AM. I cant recall a measurement of this importance being taken under such circumstances. Incredible.

The researchers at LIGO used to secretly and deliberately disturb the mirrors to test the detector. They would write down when they did it and sealed it in an envelope. When a detection was made, word would go around to see if anybody tampered with the mirrors or detector. At 4:50AM that day, nobody produced an envelope. The signal was real.

Took a while to validate the signal (and rightly so)

:D

[sjastro]

Colin,

I suspect our resident troll got the answer he was looking for.

As a two body problem the interactions between Black Holes or objects of similar mass is an extremely difficult exercise in GR given it is a non linear theory.
GR "works" as a two body problem if there is sizeable difference in mass, such as Mercury's orbit.
In this case Mercury is treated as a point mass, and space time curvature is contributed from solar gravity.

GWs are split into two problems, one is how GWs are created, the other is how they propagate through space time. The propagation is the "relatively" easy part that can be handled by GR.

The creation of GWs by merging BHs is an entirely different matter and requires Numerical Relativity (https://en.wikipedia.org/wiki/Numerical_relativity) and tons of supercomputer time processing to come up with an answer.
In essence how BHs interact with each other is answered by mathematical modelling, computer algorithms as well as advances in computer hardware.

There is no simple answer to the question.

Regards

Steven

[Eratosthenes]

I will check with xelas, but I think you will find that the modelling of the collision and merging of two black holes has nothing to do with access to supercomputers or the limitation of Numerical methodologies. Any scientist or mathematician worth their salt understands that the accuracy and applicability of Numerical simulations are grounded in the extent to which the mechanisms of the system/process are understood as well as the assumptions made.

In any case Black Hole collisions have already been simulated and these simulations require a lot less computer time and grunt than Climate and weather modelling simulations. The problem with singularity simulations and their theoretical descriptions is obtaining data and observations from nature in order to validate the models - after all the coupling and inter-validation of observation and theory is the most important pillar of the scientific method.

Its a little bit like String Theory which is more of a mathematical philosophy rather than a scientific idea due to its inherent lack of observational data to support it (so far). ST is closer to Catholicism than it is to Thermodymanics.

It's becoming more and more common for scientists to drift into the realm of religious fundamentalism as they pray in their temples everyday and chant the verses from their Scriptures like subserviant corproatised state puppets.

I hope xelas is able to forgive your little error

:D

[Shiraz]

Oh for heavens sake - this cracked record is getting distinctly boring

[xelasnave]

So tell me Peter how do we fix the problem

[xelasnave]

and Peter it seems that you do have a problem.
This constant ranting has become as Ray says somewhat like a broken record.
Your rants worry me. I worry you are not well.
Can I help if you need a friend I am here for you.

[sjastro]

That is a very admirable attitude Alex.
As a result I won't respond to his latest post.

[Eratosthenes]

I think you will find that most exams are boring, but the candidates must still try to maximise the marks they receive for each question. Bruce didnt do well with Q3 unfortunately. Although I must say that I was refreshingly surprised with the candor and honesty displayed by Colin. Bonus marks there for sure.Well done Colin!

:D

[Eratosthenes]

which problem are you referring to xelas?

Well done by the way xelas, well done on your tireless efforts in this particular forum.

[xelasnave]

Well its this way Peter your attacks rants and insults are disruptive. You seem like a nice enough bloke and quiet intelligent but you persist in behaviour that is upsetting to members.
So I wonder why you lash out the way you do.
I could speculate upon your reasons and when I do I think you are suffering some hurt that causes you to act in an anti social manner.
You could think about that and ask yourself if your personal image of yourself is well served given you choose to alienate folk with specific insults and generalizations as to the science and its short falls.
You may feel inadequate or superior I don't know.
But I ask you please be decent.
If you want insult me I will be a non moving target..and if that helps you recover your self esteem I will be happy for you.
But I ask again please don't insult people and rant about scienc.

[Eratosthenes]

I see xelas.

I will need to review your comments in more detail.

This review shouldnt take more than 9 or 10 months, so I will see you all back here, same time, same channel in early 2017.

:D

[Shiraz]

Some more details on the second candidate event (a binary BH 23 +13 merger) are at https://dcc.ligo.org/public/0123/P1500269/012/LIGO-P1500269_GW150914_CBC_Search.pdf
This paper gives a comprehensive summary of the signal processing - very interesting methodolgy. Also interesting that signal strength is now being discussed in audio terms - loudnenss. The paper points out the fundamental problem in determining noise statistics in this task - there is no way to isolate the system from GW signals and just look at noise (nothing can shield against GWs).

"Both analyses reported a candidate event on October 12, 2015 at 09:54:43 UTC as the second-loudest event in the observation period,
which we refer to as LVT151012. This candidate event has
a combined matched-filter SNR of 9.6. The PyCBC analysis
reported a false alarm rate of 1 per 2.3 years and a corresponding
false alarm probability of 0.02 for this event. The
GstLAL analysis reported a false alarm rate of 1 per 1.1 years
and a false alarm probability of 0.05. These results are consistent
with expectations for candidate events with low matched-
filter SNR, since PyCBC and GstLAL use different ranking
statistics and background estimation methods. Detector characterization
studies have not identified an instrumental or environmental
artifact as causing this candidate event [14], however
its false alarm probability is not sufficiently low to con-
fidently claim the event as a signal. It is significant enough
to warrant follow-up, however. The results of signal parameter
estimation, shown in Table I, indicate that if LVT151012
is of astrophysical origin, then the source would be a stellarmass
binary black hole system with source-frame component
masses 23+18
−5 M and 13+4
−5 M. The effective spin would be
χeff = 0.0
+0.3
−0.2
and the distance 1100+500
−500 Mpc.

[silv]

I LOVE how the first two pages list the co-authors :rofl:
How wonderful that in our age of the internet, those names won't be falling off the table like in the olden days, when the fourth author already got no reference anymore, library-wise, and was forgotten, forever.

Interesting and again exciting that the coinciding gamma ray blast was found when crawling back through the data.
and then again, was not found by the other data set. intriguing. yay. :)

Maybe Fermi detected the influx from our own sun?
It sure is close to the event time of 9.50 UTC:


quoted from ftp://ftp.swpc.noaa.gov/pub/alerts/ , specifically alerts_201509.html - a rather active period as the attached graph from the same archive shows.

I can only assume that a "Continued Alert" is actually triggered by a new overstepping of certain thresholds. I assume that based on the fact that the continuation alerts come with different time stamps as can also be seen in the graph.
In which case, in the morning, just before 10.11UTC, incoming "stuff" from our sun has triggered this NOAA alarm. and it might be what the Fermi data back crawl team has found in their data, too.
If the Fermi-measurement was anything above normal background noise, of course.

[silv]

unrelated:
From the Max Planck response to the find:
"While supermassive black holes are often accompanied by substantial disks, black holes of stellar mass lose the disk created during the progenitor star collapse on a time scale of the order of τdisk ∼ 100 s."
In my association this connects to the dumbell-explanation of a single star source for the 2 BH and how quickly this dumbell-forming and colliding would happen.

Here, the two very short-lived accretion disks might have very quickly amassed enough to stream the stuff off into the void...just before they die in each other's arms,
to form a new BH.
There's a bit of tragic cosmical romance or a little soft-porn in it, don't you think? ;)